Guard for a high voltage electrical terminal bushing

ABSTRACT

A guard for a high voltage terminal bushing includes a generally circular planar isolating member of an electrically insulating material which is mounted on the upper surface of the bushing and provided with a plurality of openings through which wind and rain may freely pass. A radial diameter of the isolating member is sufficient to prevent small animals from contacting a high voltage cable connected to the bushing and ground potential. A cylindrical section extends downwardly from the isolating member to support the guard on the upper surface of the bushing. A second cylindrical member extends downwardly and surrounds the upper portion of the bushing to form a cap to protect and shield the terminal end of the bushing. A lightning arrestor may be included which extends from adjacent the high voltage terminal to a point adjacent a transformer housing or ground potential.

BACKGROUND OF THE INVENTION

This invention relates to a guard for bushing terminals for high voltagecables. The guard may be installed not only on transformer bushings buton high-line or transmission bushings and also riser bushings. The guardis installed on the upper surface of the bushing and surrounds the highvoltage cable to prevent small animals from contacting both the highvoltage line and the transformer housing or ground potential.

In one form of a bushing terminal guard, shown in U.S. Pat. No.2,263,319, a cup-shaped member of insulating material is placed over thehigh voltage terminal and includes openings in its side walls toaccommodate the high voltage cable. The guard is mounted on the bushingby means of inwardly extending radial fins. This device only covers theend of the bushing and does not prevent a small animal standing on thetransformer housing from contacting the high voltage lead.

Another prior art device, shown in U.S. Pat. No. 2,414,732, is in theform of a sheet which is placed over an exposed high voltage member toprevent birds from perching thereon and pecking at adjacent groundedportions, thus causing short circuits. This device, however, is onlysuitable to prevent birds from resting on an energized portion of thetransformer, and it would not prevent small animals, such as squirrels,from creating a short circuit path between a high voltage cable andground.

SUMMARY OF THE INVENTION

In the present invention, a guard for bushing terminals for high voltagecables includes an isolating member of an electrically insulativematerial which is mounted on the upper surface of the bushing and isprovided with an opening through which a high voltage cable may freelypass. The isolating member is preferably planar and circular and isprovided with a plurality of openings or holes through which wind andrain may freely pass. This open construction prevents birds frombuilding nests in the protected area under the planar member. The radialdimension of the isolating member is large enough to prevent smallanimals, such as squirrels or birds, from simultaneously contacting thehigh voltage cable and ground potential.

In a preferred embodiment, a short cylindrical section extendsdownwardly from the isolating member and rests upon the upper surface ofthe bushing. A second cylindrical member coaxial with the firstcylindrical member, extends downwardly from the isolating member andsurrounds the upper portion of the bushing thereby to form a cap whichcompletely protects and shields that portion of the bushing which hasexposed metal thereon. The isolating member and both cylindrical membersmay be formed integrally of an insulating plastic material.

When the invention briefly described above is used on a transformer, forexample, a small animal standing on the transformer housing cannot,because of the isolating member, reach upwardly from the transformer andacross the isolating member to contact the high voltage cable. On theother hand, an animal sitting on the upper surface of the isolatingmember cannot simultaneously contact the high voltage cable and thetransformer housing

The guard may also be provided with a lightning arrestor comprising anelectrically conductive wire extending radially on the upper surface ofthe isolating member, with one end of the wire positioned in closeproximity to but not in contact with the high voltage cable or aconnector attached thereto. The other end of the wire extends downwardlyinto close proximity to but spaced from the transformer housing orground potential.

It is therefore an object of this invention to provide a guard forbushing terminals for high voltage cables including an isolating memberof electrically insulating material having means forming an opening inthe center thereof coaxially aligned with the bushing, said isolatingmember having a minimum radial dimension large enough to prevent smallanimals from simultaneously contacting the high voltage cable and groundpotential, means forming a plurality of openings through said isolatingmember for permitting wind and rain to pass freely therethrough, andmeans for securing said guard onto the bushing.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view showing a guard constructed according tothis invention installed on a transformer bushing terminal;

FIG. 2 is a cross-sectional view of a bushing guard constructedaccording to this invention; and

FIG. 3 is a plan view of the bushing guard of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the preferred form of the invention, as shown in FIGS. 1-3, a guard10 includes a generally planar isolating member 15 having a plurality ofsmall openings 16 formed therein, the purpose of which will be discussedlater, the isolating member being preferably circular in shape and of adimater sufficient to prevent a small animal from contacting both atransformer housing 17 and a high voltage line 20.

As shown in FIG. 1, a transformer housing 17 is shown with a bushingterminal 25 extending upwardly therefrom. This bushing 25 is ofsufficient length to prevent arcing between a high voltage line 20 whichis connected to and through the insulator to the transformer containedwithin the housing. The upper surface of the bushing 25 normallyincludes an exposed terminal assembly 26. The high voltage line isconnected to the terminal by conventional means which form no part ofthe present invention.

The guard 10 is provided with means defining an opening 27 through whichthe high voltage line 20 extends into the transformer bushing. A clamp30 is secured to the line 20 to prevent the guard 10 from movingupwardly and away from the busing 25. The clamp 30 could take the formof a split bolt 31 secured to the wire by nut 32.

As shown in FIG. 2, a cylindrical inner member 35 rests on the uppersurface of the bushing 25 and surrounds the terminal assembly 26. Asecond, longer cylindrical member 40 extends downwardly from theisolating member 15 a distance sufficient to prevent any animal fromreaching inside and possibly contacting the high voltage terminalassembly 26. The diameter of this second cylindrical member is such thatit provides a close clearance with the insulator or bushing.

The isolating member 15 is preferably circular, although it should beunderstood that any shape can be used as long as the minimum radialdimension is sufficient to prevent short circuiting of the high voltagecable 20 by small animals.

A plurality of openings 16 are formed in the member 15, as best seen inFIG. 3, to allow rain, snow and other forms of precipitation to passthrough the upper member, thereby preventing accumulation ofprecipitation on the upper surface thereof, and more importantly toprevent birds and other small animals from building nests in theotherwise protected area beneath the member 15.

A lightning protector is also provided in the preferred form of thisinvention, and includes a wire 45 having its upper end 46 spaced fromthe high voltage line 20 or the clamp 30, the wire extending radiallyoutwardly, as shown in FIG. 3, where it then descends with its lower end47 in close proximity to but not in contact with the transformer case17. The spacing of the lightning arrestor wire 45 from the wire 20 andcase 17 depend upon the voltage carried by the high voltage line, and isclose enough to allow any high voltage surges caused by lightningstrikes to be carried thereby to prevent damage to the transformer andto the bushing.

With the present invention, an animal sitting on the upper surface ofthe isolating member 15 can contact both the lightning arrestor and thehigh voltage line without coming in contact with ground potential.Similarly, an animal standing on the transformer case 17 could contactthe lightning arrestor wire 45, and not be injured because the upperpart of the lightning arrestor is not connected to the high voltageline.

It will be apparent to those skilled in the art that other forms of thisinvention can be used with all types of systems including primary,high-line, substation, and underground risers.

While the form of apparatus herein described constitutes a preferredembodiment of this invention, it is to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:
 1. A guard for an electrical bushing of the typewhich is mounted so as to extend outwardly from a member at groundpotential and which has a terminal at its upper end for connecting ahigh voltage cable, said guard being adapted for installation on theupper surface of the bushing and being of a size and shape sufficient toprevent small animals from simultaneously contacting the high voltagecable and the grounded member when installed on the upper surface of thebushing, said guard comprising:an isolating member of electricallyinsulating material having means forming an opening in the centerthereof for coaxial alignment with the bushing, said isolating memberhaving a generally planar portion having upper and lower surfaces andhaving a minimum radial dimension large enough to prevent small animalsfrom simultaneously contacting the high voltage cable and the member atground potential when the isolating member is installed on the uppersurface of the bushing, means for securng said isolating member onto thebushing, and means extending from the lower surface of said planarportion having a diameter sufficient to surround the bushing forproviding shielding for the high voltage cable and its connection tosaid bushing from beneath said isolating member when the isolatingmember is installed on the upper surface of the bushing, said generallyplanar portion of said isolating member being substantially larger indiameter than the diameter of said means extending from the lowersurface thereof.
 2. The guard of claim 1 further includingmeans forminga plurality of openings through said isolating member for permittingwind and rain to pass freely therethrough.
 3. A guard for an electricalbushing of the type which is mounted so as to extend outwardly from amember at ground potential and which has a terminal at its upper end forconnecting a high voltage cable, said guard being adapted forinstallation on the upper surface of the bushing and being of a size andshape sufficient to prevent small animals from simultaneously contactingthe high voltage cable and the grounded member when installed on theupper surface of the bushing, said guard comprising:an isolating memberof electrically insulating material having means formng an opening inthe center thereof for coaxial alignment with the bushing, said isolatngmember having a generally planar portion having upper and lower surfacesand having a minimum radial dimension large enough to prevent smallanimals from simultaneously contacting the high voltage cable and themember at ground potential when the isolating member is installed on theupper surface of the bushing, means for securing said isolating memberonto the bushing, and a first cylindrical member integrally formed withsaid isolating member and extending from the lower surface of saidplanar portion for engaging the upper surface of the bushing to spacesaid planar portion axially therefrom when the isolating member isinstalled on the upper surface of the bushing, said generally planarportion of said isolating member being substantially larger in diameterthan the diameter of said first cylindrical member.
 4. A guard asdefined in claim 3 further including a second cylindrical membercoaxially aligned with said first cylindrical member and having adiameter sufficient to surround and to extend downwardly to a pointbelow the upper surface of the bushing when the isolating member isinstalled on the upper surface of the bushing.
 5. The guard of claim 3further including means forming a plurality of openings through saidisolating member for permitting wind and rain to pass freelytherethrough.
 6. A guard for an electrical bushing of the type which ismounted so as to extend outwardly from a member at ground potential andwhich has a terminal at its upper end for connecting a high voltagecable, said guard being adapted for installation on the upper surface ofthe bushing and being of a size and shape sufficient to prevent smallanimals from simultaneously contacting the high voltage cable and thegrounded member when installed on the upper surface of the bushing, saidguard comprising:an isolating member of electrically insulating materialhaving means forming an opening in the center thereof for coaxialalignment with the bushing, said isolating member having a generallyplanar portion having upper and lower surfaces and having a minimumradial dimension large enough to prevent small animals fromsimultaneously contacting the high voltage cable and the member atground potential when the isolating member is installed on the uppersurface of the bushing, means for securing said isolating member ontothe bushing, and lightning arrestor means including an electricallyconductive wire attached to said isolating member having one endpositioned in spaced relationship to the upper surface of said planarportion for placement in close proximity to but spaced from said highvoltage cable, and the other end positioned below the lower surface ofsaid planar portion for placement in close proximity to but spaced fromthe member at ground potential.
 7. The guard of claim 6 furtherincluding means forming a plurality of openings through said isolatingmember for permitting wind and rain to pass freely therethrough.
 8. Aguard for an electrical bushing of the type which is mounted so as toextend outwardly from a member at ground potential and which has aterminal at its upper end for connecting a high voltage cable, saidguard being adapted for installation on the upper surface of the bushingand being of a size and shape sufficient to prevent small animals fromsimultaneously contacting the high voltage cable and the grounded memberwhen installed on the upper surface of the bushing, said guardcomprising:a generally planar member of electrically insulating materialhaving means forming an opening in the center thereof through which,when said planar member is installed on the upper surface of thebushing, a high voltage cable may freely pass into the bushing, saidplanar member having upper and lower surfaces and a minimum radialdimension large enough to prevent small animals from simultaneouslycontacting the high voltage cable and the member at ground potentialwhen said planar member is installed on the upper surface of thebushing, means forming a plurality of openings through said planarmember for permitting wind and rain to pass freely therethrough, a firstcylindrical member coaxially aligned with said central opening andextending from said lower surface of said planar member for engaging theupper surface of the bushing to space said planar member verticallytherefrom when said planar member is installed on the surface of thebushing, a second cylindrical member coaxially aligned with said firstcylindrical member and having a diameter sufficient to surround thebushing and a length sufficient to extend downwardly to a point belowthe upper surface of the bushing when said planar member is installed onthe upper surface of the bushing, lightning arrestor means including anelectrically conductive wire attached to said planar member and havingone end positioned in spaced relationship to the upper surface of saidplanar member for placement in close proximity to but spaced from thehigh voltage cable and the other end positioned below the lower surfaceof said planar member for placement in close proximity to but spacedfrom the member at ground potential, and means for securing said planarmember onto the bushing.
 9. The guard as defined in claim 8 wherein saidplanar member and said first and second cylindrical members areintegrally formed from an electrically insulative material.
 10. A guardfor an electrical bushing of the type which is mounted so as to extendoutwardly of a high voltage grounded transformer housing and which has aterminal at its upper end for connecting a high voltage cable, saidguard being adapted for installation on the upper surface of the bushingand being of a size and shape sufficient to prevent small animals fromsimultaneously contacting the high voltage cable and the groundedtransformer housing when installed on the upper surface of the bushing,said guard comprising:a generally circular, planar member ofelectrically insulating material having means forming an opening in thecenter thereof through which, when said planar member is installed onthe upper surface of the bushing, a high voltage cable may freely passinto the bushing, said planar member having upper and lower surfaces anda minimum radial dimension large enough to prevent small animals fromsimultaneously contacting the high voltage cable and the groundedtransformer housing when said planar member is installed on the uppersurface of the bushing, means forming a plurality of openings throughsaid planar member for permitting wind and rain to pass freelytherethrough, a first cylindrical member coaxially aligned with saidcentral opening and extending from said lower surface of said planarmember for engaging the upper surface of the bushing when installedthereon to space said planar member vertically therefrom, a secondcylindrical member coaxially aligned with said first cylindrical memberand having a diameter sufficient to surround the bushing and a lengthsufficient to extend downwardly to a point below the upper surface ofthe bushing when installed thereon, lightning arrestor means includingan electrically conductive wire attached to said planar member andhaving one end positioned for placement in close proximity to but spacedfrom the high voltage cable, said wire extending radially outwardlytoward the outer edge of said planar member and then downwardly forplacement into close proximity to the grounded transformer housing, andmeans for securing said planar member onto the bushing.